Rushing down from the north and bursting the banks of the Indus river, the rising water swallowed roads, power lines and whole villages.
Overwhelmed rescuers are having to make wrenching choices. The priority is to save women and children. Children are torn from their parents' arms
"Mom, I don't want to leave without you," one girl cries.
Her mother is allowed on board, while her father is left behind.
One-fifth of Pakistan is under water and the floods are reaching south. Some villagers tried to fight the rising tide - but most fled - joining an estimated 4 million others who are scrounging for food water and shelter.
It's a massive crisis that needs massive support. The massive support is not there yet.
The world has been slow to respond to this disaster, and desperation is starting to turn to violence.
In the town of Sukker, where up to 200,000 victims line the streets, local leaders organized a massive outdoor kitchen. From there, meals-on-wheels are sent to makeshift tent cities which are popping up everywhere.
The villagers fled to a camp on the outskirts of town. There's no running water, and they don't know when their next meal is going to come from - but they are the lucky ones. At least they have shelter.
In a nearby roadside clinic, doctors don't have time to examine their patients thoroughly. The line is long and medicine is in short supply
"We are reporting simple cases to the higher authorities that these may lead to an epidemic," said Dr. Fahim Ahmed Soomro.
One aid worker said today that the floods are "the scale of the tsunami, the destruction of Haiti and the complexity of the Middle East." Three weeks into this disaster the human tragedy is only growing.